全文获取类型
收费全文 | 3191篇 |
免费 | 48篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 322篇 |
金属工艺 | 94篇 |
机械仪表 | 63篇 |
建筑科学 | 107篇 |
矿业工程 | 10篇 |
能源动力 | 51篇 |
轻工业 | 184篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
无线电 | 138篇 |
一般工业技术 | 341篇 |
冶金工业 | 1612篇 |
原子能技术 | 13篇 |
自动化技术 | 265篇 |
出版年
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 97篇 |
2012年 | 62篇 |
2011年 | 84篇 |
2010年 | 61篇 |
2009年 | 54篇 |
2008年 | 65篇 |
2007年 | 77篇 |
2006年 | 80篇 |
2005年 | 57篇 |
2004年 | 65篇 |
2003年 | 65篇 |
2002年 | 74篇 |
2001年 | 45篇 |
2000年 | 50篇 |
1999年 | 85篇 |
1998年 | 423篇 |
1997年 | 253篇 |
1996年 | 172篇 |
1995年 | 113篇 |
1994年 | 115篇 |
1993年 | 115篇 |
1992年 | 32篇 |
1991年 | 37篇 |
1990年 | 46篇 |
1989年 | 50篇 |
1988年 | 48篇 |
1987年 | 48篇 |
1986年 | 39篇 |
1985年 | 37篇 |
1984年 | 37篇 |
1983年 | 38篇 |
1982年 | 36篇 |
1981年 | 38篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 44篇 |
1976年 | 83篇 |
1975年 | 27篇 |
1974年 | 17篇 |
1973年 | 20篇 |
1972年 | 19篇 |
排序方式: 共有3240条查询结果,搜索用时 15 毫秒
1.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
2.
KC Murray 《Canadian Metallurgical Quarterly》1994,87(3):186-187
Primary psoas abscess is a relatively rare disease with highest incidence in children and adolescents. It usually presents with fever, abdominal pain and limp. Limping tends to incriminate musculoskeletal problems below the pelvis, but movement of the hip involves the psoas muscle which is mostly retroperitoneal and intimately related to pelvic and intraperitoneal organs. Although the current tendency is to use abdominal sonography, rectal examination is still a valuable step in clinical examination, and may help to assess a pelvic mass or abscess. The following case report describes the elusive nature of psoas abscess and a rare occurrence of abscess rupture and peritonitis, immediately after rectal examination. 相似文献
3.
The pulse-stream technique, which represents neural states as sequences of pulses, is reviewed. Several general issues are raised, and generic methods appraised, for pulsed encoding, arithmetic, and intercommunication schemes. Two contrasting synapse designs are presented and compared. The first is based on a fully analog computational form in which the only digital component is the signaling mechanism itself-asynchronous, pulse-rate encoded digital voltage pulses. In this circuit, multiplication occurs in the voltage/current domain. The second design uses more conventional digital memory for weight storage, with synapse circuits based on pulse stretching. Integrated circuits implementing up to 15000 analog, fully programmable synaptic connections are described. A demonstrator project is described in which a small robot localization network is implemented using asynchronous, analog, pulse-stream devices. 相似文献
4.
NE Joseph C Fiocchi AD Levine 《Canadian Metallurgical Quarterly》1997,122(4):809-14; discussion 814-6
BACKGROUND: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC. METHODS: LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5. RESULTS: When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types. CONCLUSIONS: CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions. 相似文献
5.
6.
Murray Slovick 《今日电子》2008,(7)
石油价格攀升和全球变暖导致了人们对清洁能源的需求,2008年最常搜索的单词就是“绿色”。由于普通美国人每年直接排放的二氧化碳大约是10吨(包括家庭、汽车,以及人们旅行所排放的),而在日常生活中(购买服装、食品等)每年间接排放的大约是23吨,所以公众已经很快表现出了对绿色产品的钟爱, 相似文献
7.
8.
The effects of epithelial removal and cyclooxygenase inhibition on contractions induced by exogenous acetylcholine (ACh) and electrical field stimulation (EFS) were evaluated in horse tracheal strips and bronchial rings. Epithelial removal potentiated the response to ACh but had no influence on the response to EFS. The effect of epithelial removal was not altered by pretreating the tissues with meclofenamate, a cyclooxygenase inhibitor. In trachealis strips, meclofenamate augmented contractions induced by EFS but not by ACh. In bronchial rings, meclofenamate augmented EFS-induced contraction to a greater extent than ACh-induced contraction. These effects of meclofenamate were epithelium-independent. We conclude that horse airway epithelium produces a relaxant factor that is not a prostanoid. Endogenous prostanoids originating from non-epithelial sites inhibit only cholinergic nerves in the trachea but both parasympathetic nerves and smooth muscle in the bronchi. 相似文献
9.
JR Perry SS Deodhare JM Bilbao D Murray P Muller 《Canadian Metallurgical Quarterly》1993,32(2):157-162
Sex hormones have profound effects on immune responses and may influence the outcome of autoimmune diseases such as rheumatoid arthritis (RA). We investigated the effect of gonadal steroids on the production of interleukin-1 (IL-1) and IL-6, cytokines believed to be important in the pathogenesis of RA. Peripheral blood mononuclear cells (PBMCs) were isolated from healthy male donors and male patients with RA, and were stimulated with lipopolysaccharide (LPS) in the presence of different concentrations of 17-beta-estradiol, progesterone or testosterone. In studies of cells from normal male donors, 17-beta-estradiol at pharmacological concentrations (> or = 10(-6) M) enhanced IL-1 and IL-6 secretion as well as the production of cell-associated IL-1. Progesterone and testosterone at similar concentrations inhibited IL-1 secretion but had no significant effect on IL-6 secretion or on the production of cell-associated IL-1. In studies of male RA donors, 17-beta-estradiol failed to enhance IL-1 or IL-6 secretion and progesterone failed to inhibit IL-1 secretion. The inhibitory effects of testosterone, however, appeared to be similar to that in normal donors. It is suggested that 17-beta-estradiol may promote IL-1 and IL-6 production and release, while gestation hormone, progesterone, and testosterone may inhibit IL-1 release in vivo. These data may partly explain the gender and age differences in the incidence of RA and the development of the disease in men with low and androgen levels. 相似文献
10.
In April 1991, 91 hospitalized patients in Cairo were reported to the Egyptian Ministry of Health with botulism intoxication. To define the spectrum of illness and identify a food vehicle, 45 patients were interviewed and a case-control investigation was conducted among families of 5 hospitalized patients. Clinical specimens and specimens of implicated food were tested for toxin and cultured for Clostridium botulinum. Hospitalized patients had symptoms consistent with botulism; 18 (20%) of 91 reported patients died. Illness was associated with eating faseikh (uneviscerated, salted mullet fish; lower 95% confidence limit of odds ratio = 6.6, P < .001). All 5 case-families purchased faseikh from one shop. Very high levels of type E botulinal toxin were detected in faseikh reported to be purchased from the implicated shop; C. botulinum type E was isolated from cultures of clinical specimens and from the faseikh. This is the first documented outbreak of botulism in Egypt and the largest type E outbreak ever reported. 相似文献